Dental shade (color) matching is an important procedure in prosthetic treatment. In order to achieve the best restoration quality, dental color should be selected so that the color shows harmonic effects. Traditionally, the dentists perform the dental shade matching by visual selection using the shade tabs of the commercial dental shade guide. With such visual color selection, errors are often introduced since the visual selection heavily depends on the sense of color by individual professionals.
Recently, expensive contact-type instruments were employed in the dental practice. Most of the prior art products which employ either spectrophotometer or colorimeter for measuring color features in La*b* or HSV space.
The disadvantages of the spectrophotometer or colorimeter devices include one or more of the following.
1. They are not suitable for measuring the tooth surface that is non-flat in nature.
2. Their small view window cannot cover the whole tooth surface that provides essential information of color gradation.
3. Their algorithms are insufficient in the provision of color description of surface texture.
4. They do not provide neighboring tooth image for comparison.
5. They are difficult to be correctly positioned over the target tooth surface.
6. Only one type of color spaces is used to acquire the color information, which may be not accurate in some cases, as a result of the influence of light, environmental conditions and the like.
7. They also cannot solve the problem of metamerism effect caused by different light reflection properties between the tooth and the prosthesis materials.
Other instruments have been reported, for example, in US Patent Application No. 20030148243A1 and US Patent Application No. 20070141528A1.
In US Patent Application No. 20030148243A1, there is disclosed a dental camera and a mouthpiece attachment therefor. The camera has a light source and a light receiving element configured for receiving reflected light and producing an image based on the received light. The mouthpiece is mountable to the housing of the camera and is configured for contacting a patient's mouth for positioning the camera with respect to at least a portion of the mouth. The mouthpiece has a light channel associated with the light source for permitting the emitted light to reflect off a tooth in a patient's mouth and permitting the reflected light travel into the receiving element. A wing extends radially from the light channel and configured and dimensioned for placement between a lip and teeth of a patient for substantially blocking light from entering the light channel from outside the wing. A display on the housing is associated with the receiving element for displaying the image. A sound receiving element on the housing allows a dentist to record voice comments and stores them in connection with the images.
Another US Patent Application No. 20070141528A1 discloses a contact cap which is attached to a top cover of a camera of a dental tooth measuring apparatus, and when shooting, positioning of the tooth to be measured is performed with a bite section being slightly bitten by both of adjacent teeth sandwiching the tooth to be measured, and with keeping a state where the inside of the adjacent teeth is in contact with a camera side surface of a positioning convex section. Positioning of the tooth to be measured and the adjacent teeth with variation among individuals with respect to the camera can be performed more precisely.
Therefore, there is a need in the art for accurate dental shade matching and cost-effective fabrication of dental prosthesis.